JPH0749113Y2 - Belt transmission with automatic tension adjustment mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an improvement of a belt transmission device that automatically adjusts the tension of a timing belt according to a driving force to suppress the skip phenomenon. .

(Prior Art) Conventionally, in a belt transmission device in which a timing belt (synchro belt) is wound around a toothed pulley to perform belt transmission, when the tension of the belt decreases, the tooth portion of the belt and the tooth portion of the pulley are separated from each other. There is a problem that the mesh is lost and a so-called skip phenomenon occurs.

As a device for suppressing such a skip phenomenon, there is known a tension mechanism in which the back surface on the loose side of the belt is pressed by a tension roller urged by a spring or the like to apply a tension corresponding to the driving force to the belt. ing. However, in this structure, since the belt is bent by the tension roller in the back direction opposite to the normal bending direction, fatigue of the belt core body is promoted and the durability of the belt is deteriorated. In addition, when a large torque is applied, or when the belt stretches over time,
The return of the tension roller spring or the like reduces the pressing force, and the occurrence of the skip phenomenon cannot be reliably prevented.

In order to solve the above problems, a belt transmission device provided with an automatic tension adjusting mechanism disclosed in Japanese Patent Publication No. 58-47592 has been proposed.

That is, this proposal proposes a pair of rotating shafts that are parallel to each other, a driving and driven pulley that is composed of toothed pulleys that are respectively supported by the rotating shaft, and a space between the rotating shafts that is wound between the pulleys. A timing belt for transmitting power by means of a first pulley member that is rotatably supported integrally with a rotating shaft and has a gear on the outer periphery, and a timing belt that transmits power by an outer periphery of the first pulley member. A second pulley member that is arranged eccentrically with respect to the axis of the first pulley member, has a gear that meshes with the gear of the first pulley member on the inner circumference, and has tooth portions that mesh with the timing belt on the outer circumference; The second pulley member is provided in a slack side eccentric zone defined by a straight line connecting the shaft centers of the two rotating shafts and a straight line orthogonal to the straight line and passing through the shaft center of the first pulley member. A certain amount of axis To Kokoroshite position is obtained by setting the length of the belt.

(Problems to be Solved by the Invention) However, in this proposal, when the drive pulley side is composed of the first and second pulley members, the second pulley member side is inevitably due to the difference in diameter of the quantity pulley member. The number of gears in the first pulley member is greater than the number of gears in the first pulley member, and the rotation of the rotating shaft is decelerated and transmitted to the second pulley member, that is, the belt. For this reason, when applied to a bicycle drive system that needs to accelerate and transmit rotation from the drive pulley to the driven pulley, the diameter of the drive pulley is required in anticipation of the above deceleration amount in order to ensure the increased transmission. It must be made larger than the above, and there are problems such as a large space for disposing it and an increase in weight.

Further, since the two pulley members are meshed with each other between steel bodies, there is a problem that torque cross and noise due to friction during meshing increase and durability deteriorates due to wear. Moreover, when foreign matter enters the gear portions of both pulley members, the pulleys may be damaged.

Therefore, the present applicant has previously proposed a belt transmission device that can solve the above problems (see Japanese Patent Application No. 63-50849 and the drawings). That is, as shown in FIG. 3, this proposal has a pair of rotating shafts 1, 2 which are parallel to each other and the rotating shafts 1, 2
A drive and driven pulley 3 ', 12 each of which is supported by a toothed pulley and a timing belt B wound around the pulleys 3', 12 to transmit power between the rotary shafts 1, 2.
And a first pulley member 4'wherein the drive pulley 3'is rotatably supported by the rotating shaft 1 and a first pulley member 4'on the outer periphery of the first pulley member 4 '. It has an eccentric capable axis O ₂ with respect to the axis O _1, and 'second pulley member 5 substantially ring-shaped having a' teeth 5b meshing with the timing belt B on the outer circumference, the inner end the first 1 is connected to the outer periphery of the pulley member 4'at a predetermined angular interval,
And a plurality of high tension flexible members 6 ', 6', ... having the same length L, the outer ends of which are connected to the inner circumference of the second pulley member 5'at a predetermined angular interval. To do. The high tension flexible member 6 ', which connects the pulley members 4', 5'to each other,
In order to give looseness to 6 ', ..., each flexible member 6'
Is set to L> (D _I −D _O ) / 2 with respect to the outer diameter D _{O of} the first pulley member 4 ′ and the inner diameter D _{I of} the second pulley member 5 ′.

By the way, in general, when connecting a high tension body and a rigid body,
Although the strength and durability of the high-tensile body of the connecting portion are problems, the above-mentioned proposals also have similar problems. That is, as a structure in which each of the high tension flexible members 6 ', 6', ... Is connected to the pulley members 4 ', 5', for example, each flexible member 6'is sandwiched by chucking portions. A structure in which the two pulley members 4'and 5'are connected to each other is conceivable, but in that case, the strength and durability of the flexible member 6'at the chucking portion are significantly deteriorated, which causes a problem in practical use. Moreover, it is necessary to dispose the chucking portions at a plurality of positions in the circumferential direction of the pulley members 4'and 5 ', and it is unavoidable that the structure of the drive pulley 3'becomes complicated, and there is room for further improvement. It was

The object of the present invention is to improve the strength of the flexible member at the connecting portion by improving the structure of the high-strength flexible member and the connecting structure for the first and second pulley members in the above belt transmission. It is to improve the durability and at the same time to simplify the structure of the drive pulley.

(Means for Solving the Problem) In order to achieve this object, the solution means of the present invention is to use endless endless high tension flexible members, with engaging portions at equal intervals. They are formed and are alternately engaged and fixed to the first and second pulley members, respectively.

Specifically, the invention according to claim (1) is such that a pair of rotating shafts parallel to each other, a driving and driven pulley formed of toothed pulleys supported by the rotating shafts respectively, and a winding between both pulleys. It is premised on a belt transmission device provided with a timing belt which is hung and transmits power between both rotary shafts.

Further, the drive pulley has a first pulley member that is rotatably supported integrally with a rotating shaft, and a center hole that allows the first pulley member to be loosely fitted, and the center hole allows the first pulley member to rotate. A substantially ring-shaped second pulley member, which is arranged on the outer periphery so as to be eccentric with respect to the axis of the first pulley member and has a tooth portion that meshes with the timing belt on the outer periphery, and an endless device that rotatably connects the two pulley members together. And a high tension flexible member.

Further, the endless high tension flexible member is provided with a plurality of engaging projections at equal intervals in the length direction.

On the other hand, a plurality of engagements for engaging the engagement protrusions of the endless high tension flexible member with the outer periphery of the first pulley member and the inner periphery of the second pulley member to connect the flexible member to the pulley member. A concave portion and a plurality of guide groove portions that guide the flexible member on the side of the engaging protrusion are provided at predetermined angular intervals in the circumferential direction.

The engaging projections of the flexible member are alternately engaged with the engaging recesses of the first and second pulley members over the entire circumference.

(Operation) With the above configuration, in the present invention, the tension of the timing belt becomes zero in the unloaded state, and the axial centers of both pulley members in the drive pulley are displaced by the maximum amount. Also, the high-tensile flexible member is loosened in its span. Then, when a driving force is applied to the rotary shaft from this state and a load state is reached, the positional relationship between the pulley members and the span of the high tension flexible member continuously changes according to the driving force, and the flexible When the span of the flexible member crosses substantially the belt loosening side with respect to the straight line connecting the shaft centers of the rotating shafts in the plane passing through the shaft centers of the pulley members, the span of the flexible member becomes in a tension state, and The driving force is transmitted from the first pulley member to the second pulley member via the flexible member. At this time, as a component force of the force transmitted to the flexible member, a force for moving the second pulley member to the tension side of the timing belt along a plane passing through the shaft centers of both pulley members works together with the driving force. By this force, the eccentric amount of both pulley members changes in the decreasing direction, the second pulley member moves in the direction of increasing the belt pitch circumferential length, and accordingly, the tension side and the slack side of the belt are always constant. The tension is distributed at a ratio of, and thus the belt skip phenomenon can be effectively suppressed. Then, when the belt is running, the shaft centers of the two pulley members substantially coincide with each other, which causes the drive pulley to rotate smoothly.

In that case, when a large tension is applied to the flexible member by the driving force applied to the driving pulley, the frictional force in the guide groove of the pulley member of the flexible member and the engaging recess of the engaging protrusion The driving force is transmitted from the first pulley member to the second pulley member by the engagement with the. Therefore, unlike the case where the flexible member is sandwiched by the chucking portions, unnecessary stress concentration is eliminated, so that the strength and durability of the high tension flexible member at the connecting portion can be increased.

Moreover, when a large driving force is applied, the engagement protrusion of the flexible member elastically deforms in the engagement recess of the pulley member.
Along with this elastic deformation, the driving force is shared by a plurality of spans of the flexible member, and the durability against a large driving force can be favorably maintained.

Further, since the flexible member is alternately engaged with the pulley member, the structure of the drive pulley is not complicated and the simplification thereof can be achieved.

Further, since both pulley members are connected by the span of the high tension flexible member, the rotation of the rotary shaft can be transmitted to the drive pulley at a transmission ratio of 1: 1 to accelerate the rotation of the drive pulley. Even when the drive pulley is transmitted to the driven pulley, the drive pulley does not have to be made larger than necessary, so that the arrangement space of the drive pulley can be reduced and the weight thereof can be reduced.

In addition, since the driving force is transmitted between the two pulley members by the connection with the flexible member in this way, friction torque and noise are lower than in the case where the driving force is transmitted by gear engagement etc., and wear is suppressed and durability is reduced. The pulley member is less likely to be damaged even if foreign matter is mixed between the pulley members.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. still,
The basic structure of the belt transmission device according to this embodiment is the same as that shown in FIG. 3, and the same parts as those in FIG. 3 are designated by the same reference numerals and the detailed description thereof will be omitted.

That is, FIG. 2 shows an overall configuration of an embodiment in which the present invention is applied to a bicycle drive system, including a drive shaft 1 connected to a bicycle crank pedal (not shown) and a bicycle rear wheel (not shown). ) Are arranged in parallel with each other, and a drive pulley 3 having teeth is attached to the drive shaft 1 so as to rotate together. On the other hand, the driven shaft 12 has a driven pulley 12 having a smaller diameter than the driving pulley 3 and having teeth 12a on the outer periphery, which is integrally rotated only in the driving rotation direction (counterclockwise direction in the drawing) via a one-way clutch mechanism (not shown). Is supported as. A timing belt B having a tooth portion B ₁ on the bottom surface (inner peripheral surface) is wound between the pulleys 3 and 12, and the belt B transmits power from the drive shaft 1 to the driven shaft 2. It is done like this.

The drive pulley 3 has a first pulley member 4 rotatably and integrally supported by the drive shaft 1, and a central hole 5a arranged on the outer periphery of the first pulley member 4 and into which the first pulley member 4 can be loosely fitted. A substantially ring-shaped second pulley member 5 having an axial center O ₁ of the first pulley member 4, that is, an axial center O ₂ eccentrically with respect to the rotation center of the drive shaft 1; 1 to connect
This is composed of an endless belt 6 as a book endless high tension flexible member, and a tooth portion 5b meshing with the timing belt B is formed on the outer periphery of the second pulley member 5. For the first and second pulley members 4 and 5, it is preferable to use a molded product such as a resin injection molded product or an aluminum die cast molded product by a molding die.

The endless belt 6 is in the form of a transmission belt in which a tensile body is embedded in an elastic body. And the bottom surface (inner surface)
, Are formed with eight engaging projections 7, 7, ... That project in the inner circumferential direction thereof at equal intervals in the length direction.

On the other hand, the outer periphery of the first pulley member 4 is engaged with four of the eight engaging protrusions 7, 7, ... , And four guide groove portions 9, 9 for guiding the endless belt 6 on the side of each of the engagement projections 7 are circumferentially 90
They are provided at equal angular intervals of °. In particular,
Each of the guide groove portions 9 is recessed in four equal positions on the outer periphery of the side surface of the pulley member 4, and both ends thereof are opened on the outer peripheral surface of the pulley member 4 so that the opening area smoothly expands toward the groove end portion. There is. Then, the side surface on the pulley shaft center O ₁ side in the center of the groove portion 9 is cut out, and the engagement concave portion 8 is formed by the cutout.

Further, the endless belt 6 is provided on the inner circumference of the second pulley member 5.
, Which engage with the remaining four engaging projections 7, 7, ... To connect the belt 6 to the second pulley member 5,
Four guide groove portions 11, 11, ... Which guide the endless belt 6 on the side of each of the engaging projections 7 are provided at equal angular intervals of 90 ° in the circumferential direction. The guide groove portions 11 are similar to the guide groove portions 9 of the first pulley member 4 in the pulley member 5.
Are formed at four equally spaced positions on the outer periphery of the side surface of the pulley member 5, and both ends thereof are opened on the inner peripheral surface of the pulley member 5 so that the opening area smoothly expands toward the groove end portion. And the groove 11
A side surface of the central portion on the outer side in the radial direction of the pulley is cut out, and the engaging recess 10 is formed by the cutout.

Therefore, the engaging recesses 8, 8 of the first and second pulley members 4, 5,
8, ... and 10,10, .. are engaging projections 7,7, of the belt 6, respectively.
Are alternately engaged with each other over the entire circumference, and both pulley members 4 and 5 are connected by the endless belt 6 by this structure.

A straight line connecting the axes O ₁ and O _{3 of the} drive and driven shafts 1 and 2
and l _A, the straight line l perpendicular to _A and the straight line l _B and slack side eccentric zones partitioned by Z through the axis O ₁ of the first pulley member 4, the axis O of the second pulley member 5 The length of the timing belt B is set so that ₂ is located eccentrically by a predetermined amount.

Therefore, in the above-described embodiment, the tension of the timing belt B becomes zero and the axial center O ₂ of the second pulley member 5 in the drive pulley 3 becomes zero in the no-load state in which power is not transmitted between the pulleys 3 and 12. Is eccentric to the axial center O ₁ of the first pulley member 4 by the maximum amount.

When the driving force of the driving shaft 1 is applied from this state to the loaded state, the positions of the second pulley member 5 and the spans of the endless belt 6 continuously change according to the driving force, and each span is On a plane p passing through the shaft centers O ₁ and O ₂ of the first and second pulley members 4 and 5, the timing belt B is almost aligned with the straight line l _A connecting the shaft centers O ₁ and O ₃ of the drive and driven shafts 1 and 2. When crossing the slack side range (lower right side in the figure), the spans become in tension, and the driving force is transmitted from the first pulley member 4 to the second pulley member 5 via the span. At this time, as a component force of the force transmitted to the endless belt 6, in addition to the driving force, the second pulley member 5 is moved along the plane p passing through the axial centers O ₁ and O ₂ of the first and second pulley members 4,5. As a result, a force to move the timing belt B toward the tensioned side acts, and the second pulley member 5 is pulled by the endless belt 6 in the tensioned state so that the amount of eccentricity with the first pulley member 4 decreases. The belt moves toward the belt tension side (the direction in which the belt pitch circumference is increased), and accordingly, a constant tension is always distributed to the tension side and the slack side of the timing belt B. As a result, the skip phenomenon of the timing belt B can be suppressed.

In the traveling state of the timing belt B, the shaft centers O ₁ and O _{2 of the} pulley members 4 and 5 substantially coincide with each other, which allows the drive pulley 3 to rotate smoothly.

In that case, when a large tension is applied to the endless belt 6 by the driving force applied to the driving pulley 3, the frictional force in the guide grooves 9 and 11 of the pulley members 4 and 5 of the endless belt 6 and the The driving force is transmitted from the first pulley member 4 to the second pulley member 5 by the engagement of the engagement protrusion 7 with the engagement recesses 8 and 11. Therefore, unlike the case where the endless belt is clamped by the chucking portion, unnecessary stress concentration is eliminated,
The strength of the endless belt 6 is not significantly reduced at the connecting portion, so that the strength and durability can be improved.

Moreover, when a large driving force is applied, each engagement protrusion 7 of the endless belt 6 is elastically deformed in the engagement recesses 8 and 10 of each pulley member 4,5. Due to this elastic deformation, the driving force is shared by the eight spans of the endless belt 6, and the durability against a large driving force can be favorably maintained.

Further, since the endless belt 6 has a structure in which the first and second pulley members 4 and 5 are alternately engaged with each other, the structure of the drive pulley 3 does not become complicated and can be simplified. In particular,
It is more preferable to use a molding product such as a resin injection molding product or an aluminum die-cast molding product for the two pulley members 4 and 5, because the structure is simple and the cost is low.

Further, since the pulley members 4 and 5 are connected by the endless belt 6, the rotation of the drive shaft 1 can be transmitted to the drive pulley 3 at a transmission ratio of 1: 1 to accelerate the rotation of the drive pulley 3. Therefore, even when the drive pulley 3 is transmitted to the driven pulley 12, it is not necessary to make the drive pulley 3 larger than necessary, so that the arrangement space of the drive pulley 3 can be reduced and the weight thereof can be reduced.

Further, since both pulley members 4 and 5 in the drive pulley 3 are connected by the endless belt 6 to transmit the driving force, compared with the case where the driving force is transmitted by gear engagement or the like,
Friction torque and noise are suppressed to a low level, wear is reduced, and even if foreign matter enters between the pulley members 4 and 5, the pulley members 4 and 5 can be prevented from being damaged.

In addition, since the tension of the timing belt B is zero in the unloaded state, it is not necessary to apply the initial tension when the timing belt B is attached, and the attachment can be easily performed.

In the above embodiment, the number of engaging protrusions 7 of the endless belt 6 is set to 8, and the engaging recesses 8 and 10 (guide grooves of both pulley members 4 and 5) are provided.
Although the numbers 9 and 11) are each set to 4, it is needless to say that these numbers may be changed to a plurality of other numbers.

Further, the above embodiment is applied to the drive system of the bicycle, but the present invention can also be applied to various belt transmissions which require high durability.

(Effects of the Invention) As described above, according to the present invention, a drive pulley for transmitting power between a driven pulley and a driven pulley by a timing belt, and a first pulley member rotatably supported by a rotary shaft thereof. The first pulley member has a center hole through which the first pulley member can be loosely fitted, and the center hole allows the first pulley member to be eccentrically arranged with respect to the outer periphery of the first pulley member. The second pulley member is connected via a tension flexible member and meshes with the timing belt on the outer periphery, and the engaging protrusion of the flexible member is engaged with the engaging recess of each pulley member via the guide groove. The flexible member and the pulley member are engaged with each other, and the eccentric amount of the second pulley member with respect to the first pulley member is continuously decreased as the driving force of the first pulley member increases. The first pulley The rotation of the member can be transmitted to the second pulley member at a rotation ratio of 1: 1 and the diameter of the drive pulley can be kept small even in a drive system that accelerates the rotation of the drive pulley and transmits it to the driven pulley.
Therefore, it is possible to reduce the space for arranging the drive pulley and further the belt transmission device, and to reduce the weight. In addition, by connecting both pulley members with a high tension flexible member, friction torque, noise, wear, etc. can be reduced, and damage due to foreign matter mixing in the state of driving force transmission between both pulley members is suppressed, and its durability is improved. Can be improved. further,
It is possible to suppress the stress concentration at the connecting portion of the flexible member with the pulley member, to enhance the strength and durability thereof, and consequently to improve the durability of the belt transmission device. In addition, the structure of the drive pulley can be simplified by engaging and fixing the flexible member.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention, FIG. 1 is an enlarged front view of a drive pulley, and FIG. 2 is a partially cutaway front view of a belt transmission. FIG. 3 is a view corresponding to FIG. 2 showing a comparative example of the belt transmission device. 1 …… Drive shaft (rotating shaft) 2 …… Driven shaft (rotating shaft) 3 …… Drive pulley 4 …… First pulley member 5 …… Second pulley member 5a …… Center hole 5b …… Tooth portion 6 …… Endless belt (endless high-tensile flexible member) 7 ... Engagement protrusions 8, 10 ... Engagement recesses 9, 11 ... Guide groove 12 ... Driven pulley 12a ... Tooth B ... Timing belt

Claims (1)

[Scope of utility model registration request] 1. A pair of rotating shafts which are parallel to each other, a drive and a driven pulley which are toothed pulleys which are respectively supported by the rotating shafts, and a power supply between the rotating shafts which is wound between the two pulleys. A timing belt for transmission, and the drive pulley includes a first pulley rotatably supported on a rotary shaft.
A pulley member and a center hole through which the first pulley member can be loosely fitted, and the center hole is arranged on the outer periphery of the first pulley member so as to be eccentric with respect to the axis of the first pulley member;
A substantially ring-shaped second pulley member having a tooth portion that meshes with the timing belt on the outer periphery, and an endless high tension flexible member that connects the pulley members to each other in a rotationally integrated manner are provided. On the elastic member, a plurality of engaging protrusions are provided at equal intervals in the length direction, while on the outer periphery of the first pulley member and on the inner periphery of the second pulley member, the endless high tension flexible member is formed. A plurality of engaging recesses that engage the engaging protrusions to connect the flexible member to the pulley member and a plurality of guide groove portions that guide the flexible member on the side of the engaging protrusions are circumferentially predetermined. The engaging protrusions of the flexible member are alternately engaged with the engaging recesses of the first and second pulley members over the entire circumference. Belt transmission with automatic tension adjustment mechanism.